Interfacial Carbon Nanoplatelet Formation by Ion Irradiation of Graphene on Iridium(111)

Abstract

We expose epitaxial graphene (Gr) on Ir(111) to low-energy noble gas ion irradiation and investigate by scanning tunneling microscopy and atomistic simulations the behavior of C atoms detached from Gr due to ion impacts. Consistent with our density functional theory calculations, upon annealing Gr nanoplatelets nucleate at the Gr/Ir(111) interface from trapped C atoms initially displaced with momentum toward the substrate. Making use of the nanoplatelet formation phenomenon, we measure the trapping yield as a function of ion energy and species and compare the values to those obtained using molecular dynamics simulations. Thereby, complementary to the sputtering yield, the trapping yield is established as a quantity characterizing the response of supported 2D materials to ion exposure. Our findings shed light on the microscopic mechanisms of defect production in supported 2D materials under ion irradiation and pave the way toward precise control of such systems by ion beam engineering.

Annealing of ion-irradiated hexagonal boron nitride on Ir(111)

“…Since the edge atom binding energy to the substrate in a favorable geometry is of the order of 2 eV per atom [26], the enormous stability of the vacancy clusters becomes understandable. We note that a similar pinning of vacancy clusters to specific moiré sites was also found for graphene on Ir(111) [40,47]. However, for graphene on Ir(111), the vacancy clusters are thermally less stable (only up to 1000 K) and the location within the moiré unit cell is not uniquely defined.…”

“…Thus, no quasiequilibrium between a 2D gas phase of its constituents and the h-BN layer on Ir(111) can be established. To the contrary, C monomers and small C clusters are extremely stably bound to Ir(111) without any chance to desorb [40]. Therefore, there is a temperature regime, extending beyond the stability range of h-BN, where small adsorbed carbon entities coexist with the Gr sheet.…”

“…In the past few years, ion-induced damage and annealing of Gr on a metal substrate has been intensely investigated: trapping of single noble gas ions under Gr on Ru(0001) [38]; formation of highly pressurized gas blisters under Gr on Pt(111) [39], Ir(111) [40][41][42], Ir(100) [43], and Ni(111) [44,45] upon annealing subsequent to noble gas implantation, damage evolution with ion energy [46]; formation of a regular arrangement of vacancy clusters with moiré periodicity (nanomesh) [47]; interface channeling [47]; and sputter protection of the substrate through a Gr cover [48]. In these studies, room-temperature irradiated Gr demonstrated a remarkable ability to self-repair upon annealing, which one might relate to the flexible bond reorganization in this material.…”

Xe irradiation of graphene on Ir(111): From trapping to blistering

“…3(a). Due to Gr sputtering, such edges are formed in large number during irradiation and annealing, but Gr dangling bonds are saturated due to the strong interaction of Gr with the metal giving rise to bending of the sheet towards the metal surface already at room temperature 25,38 . The energy of the system as a function of the coordinate of the Xe atom along the path is presented in Fig.…”

“…For low energies and fluences (negligible damage), Cun et al [20][21][22][23] demonstrated that implanted Ar + ions may come to rest under a 2D-layer strongly adhering to a metal surface and remain there upon annealing. In a recent comment 24 to a paper by Herbig et al 25 , we pointed out that Xe + irradiation of Gr on Ir(111) is accompanied by Xe trapping at the interface.…”